JP4883174B2 - Mass spectrometer - Google Patents

Description

  The present invention relates to a mass spectrometer used in a liquid chromatograph mass spectrometer and the like, and more particularly to an ion transport optical system for transporting ions to a subsequent stage in the mass spectrometer.

  In mass spectrometers, ion transport optics called ion lenses and ion guides are used to converge ions that are sent from the front stage and, in some cases, accelerate and send them to a subsequent mass analyzer such as a quadrupole mass filter. A system is used. As one of such ion transport optical systems, a multipole rod type such as a quadrupole or an octupole has been conventionally used. FIG. 10A is a schematic perspective view of a general quadrupole rod type ion guide.

  This ion guide 70 has a structure in which four rod electrodes 71, 72, 73, 74 having a columnar (or cylindrical) shape are arranged in parallel to each other so as to surround the ion optical axis C. In general, the same high-frequency voltage is applied to the two rod electrodes 71 and 73 facing each other across the ion optical axis C, and the two rod electrodes 72 and 74 adjacent in the circumferential direction are first applied to the two rod electrodes 71 and 73. A high-frequency voltage having the same amplitude and reversed phase is applied. A quadrupole high-frequency electric field is formed in the space surrounded by the four rod electrodes 71, 72, 73, 74 by the high-frequency voltage applied in this way, and the ion optical axis C is generated while vibrating ions in this high-frequency electric field. It can be transported to the later stage while converging in the vicinity.

  The applicant of the present application is shown in a perspective view of FIG. 10B as an ion transport optical system capable of accelerating ions while taking advantage of the above-mentioned multipole rod type ion guide that ion convergence is good. An ion transport optical system using such a virtual rod electrode has been proposed (for example, see Patent Document 1). In this configuration, each of the rod electrodes 71, 72, 73, 74 shown in FIG. 10A is arranged in a plurality of (four in this example) plate shape along the direction of the ion optical axis C. The virtual rod electrodes 75, 76, 77, 78 constituted by the electrode base plate 79 are replaced.

  In this virtual multipole rod type ion transport optical system, different voltages can be applied to the four electrode base plates 79 constituting one virtual rod electrode 75, 76, 77, 78. For example, by applying a DC voltage that increases stepwise in the direction in which ions travel so as to be superimposed on the high-frequency voltage, the ions are accelerated when passing through the space surrounded by the virtual rod electrodes 75, 76, 77, 78. Or you can decelerate. Furthermore, as shown in FIG. 10C, the electrode element plate 79 constituting the virtual rod electrode is disposed so as to approach the ion optical axis C stepwise in the ion traveling direction, thereby converging the ion flow. It can also be gradually squeezed while.

  Although the ion transport optical system using the virtual rod electrode has excellent characteristics as described above, the number of parts inevitably increases because the electrode that can be originally composed of one rod electrode is divided into a plurality of electrode base plates. Therefore, it is inevitable that adjustment during assembly, manufacture and use becomes complicated. For this problem, the applicant of the present application has proposed a specific configuration of a multipole rod type ion guide using a virtual rod electrode in Patent Document 2.

  In the configuration disclosed in this document, one electrode base plate has a slightly long shape in which one end on the side facing the ion optical axis is arcuate when completed, and the ion beam is in a plane perpendicular to the ion optical axis. Four electrode base plates arranged so as to surround the shaft are taken as one set, and four sets of electrode base plates arranged in the direction of the ion optical axis to form four virtual rod electrodes, that is, 16 electrode base plates Is attached to a synthetic resin holder which is an insulator with screws. Moreover, the electrode base plates to which the same voltage is applied and which are opposed to each other across the ion optical axis in a plane orthogonal to the ion optical axis are connected by a short line. In this way, since the main components including the electrode base plate are integrated (unitized), the handling is easy, and the labor for assembly and adjustment can be reduced.

  However, even in such a configuration, the number of electrode base plates required for the total number of virtual rod electrodes multiplied by the total number of electrode base plates constituting one virtual rod electrode is approximately quadrupole. However, as the number of poles such as hexapoles and octupoles increases, the number of parts increases, and assembling and adjustment become complicated. The same applies when the number of electrode base plates constituting one virtual rod electrode is increased to, for example, 10 or 20. For these reasons, it is desirable to further reduce the number of parts and simplify assembly and adjustment. In addition, when an individual electrode base plate is attached to a holder with a screw, a slight relative positional shift of the electrode base plate may occur at the time of attachment, which may adversely affect ion convergence, that is, ion passing efficiency. .

JP 2000-149865 A JP 2001-351563 A

  The present invention has been made to solve the above-mentioned problems, and its main object is to provide a virtual multipole rod type ion transport that facilitates assembly during manufacture and adjustment during manufacture and use. An object of the present invention is to provide a mass spectrometer equipped with an optical system.

The present invention, which has been made to solve the above problems, surrounds an imaginary optical axis with a virtual rod electrode composed of m (m is an integer of 2 or more) electrode base plate portions separated from each other in the ionic optical axis direction. In a mass spectrometer having a virtual multipole rod type ion transport optical system in which 2n (n is an integer of 2 or more) are arranged as described above,
The n electrode base plate portions that belong to every other virtual rod electrode around the ion optical axis and are arranged in a plane orthogonal to the ion optical axis are electrically connected to the n electrode base plate portions. Are formed integrally with one conductive plate as an electrode member, and the electrode members are arranged 2 m apart from each other in the direction of the ion optical axis, thereby arranging the virtual multipole rod ion transport optical system. It is characterized by the construction.

  In a multipole rod type ion transport optical system, generally, two electrodes adjacent in the circumferential direction are applied with different voltages, for example, a composite voltage V + v · cosωt obtained by superimposing a high frequency voltage v · cosωt on a DC bias voltage V on one side. In this case, a composite voltage Vv · cosωt obtained by superimposing a high-frequency voltage −v · cosωt having a phase opposite to that of the previous high-frequency voltage v · cosωt on the same DC bias voltage V is applied. In the mass spectrometer according to the present invention, every other n electrode element plate portions around the ion optical axis are provided on a certain electrode member, and the electrode element plate portions adjacent to the periphery of the ion optical axis. They are provided on different electrode members. That is, since only n electrode base plate portions to which the same voltage is applied are provided on the same electrode member, a predetermined voltage is applied to each electrode member to create a space surrounded by 2n virtual rod electrodes. An appropriate high-frequency electric field or a composite electric field in which a high-frequency electric field is superimposed on a DC electric field can be formed. Moreover, since the several electrode base plate part and the connection part which connects these electrode base plate parts are integrated, the number of parts can be decreased.

  For example, n = 2 in the virtual quadrupole rod type ion transport optical system, and n = 4 in the virtual octupole rod type ion transport optical system. In the mass spectrometer according to the present invention, the number of electrode members to be prepared is independent of the number of poles 2n of the virtual multipole rod ion transport optical system. Therefore, even when the number of poles increases, the number of electrode members to be prepared is the same as long as the number of electrode base plate portions constituting one virtual rod electrode does not change. As described above, according to the mass spectrometer of the present invention, the number of parts for configuring the virtual multipole rod-type ion transport optical system can be suppressed, and particularly when the number of poles is large, the number of parts can be suppressed. Is big.

  As a preferable aspect of the mass spectrometer according to the present invention, the electrode member has a shape in which the electrode base plate portion extends inward from an inner edge end of the connection portion, which is a ring shape or a shape obtained by partially cutting a ring. It is good to have a configuration. Here, the ring can be, for example, an annular ring. The electrode base plate portion may be formed such that the inner side thereof, that is, the edge toward the ion optical axis is formed in an arc shape or a hyperbola shape, for example.

  In a multipole rod ion transport optical system, the angles between two rod electrodes adjacent around the ion optical axis are equal. Therefore, the two electrode members adjacent to each other in the direction of the ion optical axis, each having an electrode base plate part belonging to a different virtual rod electrode (adjacent around the ion optical axis), have exactly the same shape, and one of them is the other On the other hand, it can be obtained by rotating the ion optical axis by a predetermined angle. That is, since only one type of electrode member needs to be manufactured, the cost for manufacturing the electrode member can be suppressed, and the virtual multipole rod ion transport optical system can be configured at low cost.

Also, in the mass spectrometer according to the present invention, any one of the electrode members is one insulating holding inserted in order to separate a predetermined distance between the two electrode members adjacent in the ion optical axis direction. It can be set as the structure hold | maintained by a member.

  According to this configuration, the virtual multipole rod ion transport optical system can be easily configured by arranging the holding members holding the electrode members so as to overlap each other in the ion optical axis direction. At that time, the distance between the adjacent electrode members is determined by the thickness of the holding member in the direction of the ion optical axis, so that the electrode members can be accurately positioned. Further, since the change of the number of electrode base plate portions constituting one virtual rod electrode can be changed depending on the number of holding members to be arranged, the change is easy and the virtual multipole rod type ion transport having an arbitrary number of stages is possible. An optical system can be configured.

  In the conventional virtual multipole rod ion transport optical system as described above, one electrode base plate belonging to 2n virtual rod electrodes is necessarily included in a plane perpendicular to the ion optical axis. On the other hand, in the mass spectrometer according to the present invention, when the electrode member is formed in a flat plate shape, the electrode base plate part belonging to the virtual rod electrode adjacent around the ion optical axis is in a plane perpendicular to the ion optical axis. Is not included in the ion beam, and shifts in the ion optical axis direction. However, even in that case, since there is almost no influence on the high-frequency electric field generated in the space surrounded by the virtual rod electrode, particularly in the vicinity of the ion optical axis, sufficient ion convergence performance can be exhibited.

However, in order to improve the ion focusing performance or to change the DC voltage applied to accelerate or decelerate ions for each stage, the virtual rod electrode adjacent to the ion optical axis is applied. It is more convenient for the electrode base plate part to belong to exist in a plane orthogonal to the ion optical axis. Therefore, in the mass spectrometer according to the present invention, the 2 m pieces of the electrode members include the m first electrode members whose electrode base plate portions are flush with the connection portions, and the electrode base plate portions that are connected. And m second electrode members that are not flush with the portion, and the first electrode members and the second electrode members are arranged alternately and separated in the direction of the ion optical axis at the position of the substantially annular connecting portion. Thus, it is preferable that a total of 2n electrode base plate portions, one from each virtual rod electrode, be positioned on a plane orthogonal to the ion optical axis.

  According to the mass spectrometer of the present invention, the electrode base plate portion to which the same voltage is applied in the plane orthogonal to the ion optical axis and the connection portion corresponding to the connection wire (cable wire or the like) are provided as one electrode member. Therefore, it is only necessary to prepare twice as many electrode members as the number m of electrode base plate portions constituting one virtual rod electrode, that is, 2 m electrode members, regardless of the number of poles. Therefore, the number of parts constituting the virtual multipole rod ion transport optical system can be reduced, and adjustment during assembly, manufacture, and use can be facilitated. In particular, even if the number of poles increases, the cost and ease of assembly do not change, which is useful for increasing the number of poles. In addition, since all the 2 m electrode members can have the same shape, this is also advantageous for cost reduction.

The block diagram of the principal part of the MS / MS type | mold mass spectrometer which is one Example of this invention. The top view of the electrode member for comprising the virtual quadrupole rod type | mold ion guide arrange | positioned in a collision cell. A plan view of the electrode holder for constituting the virtual quadrupole rod type ion guide (a), a cross-sectional view taken along the line AA '(b), and a cross section taken along the line BB'. FIG. The top view (a) and longitudinal cross-sectional view (b) of the state which attached the electrode member to the electrode holder. The longitudinal section of the important section showing the electrode arrangement of a virtual quadrupole rod type ion guide. The figure which shows the result of having simulated the passage state of the ion in a virtual quadrupole rod type ion guide. The top view (a) of the electrode member for comprising the virtual quadrupole rod type | mold ion guide in the mass spectrometer of another Example, and sectional drawing in a D-D 'arrow cutting line (b). The longitudinal cross-sectional view of the principal part which shows the electrode arrangement | sequence of the virtual quadrupole rod type | mold ion guide in another Example. The top view of the electrode member for comprising the virtual quadrupole rod type | mold ion guide in the mass spectrometer of another Example. The schematic block diagram of the conventional various multipole rod type ion guide.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Nozzle 2 ... Sampling cone 3 ... 1st ion lens 4 ... 2nd ion lens 5 ... 1st stage quadrupole 6 ... Collision cell 7 ... 2nd stage quadrupole 8 ... 3rd stage quadrupole 9 ... Ion Detector C ... Ion optical axes 11, 15 ... First electrode member 12 ... Second electrode member 13 ... Electrode holder 14 ... Fixing bolts 20, 24 ... Annular parts 21, 25, 41 ... Electrode base plate parts 22, 26 ... Terminal parts 23, 27 ... Circular opening 30 ... Annular part 31 ... Flange part 32 ... Notch part 33 ... Bolt insertion hole

  An MS / MS type (tandem type) mass spectrometer that is an embodiment of a mass spectrometer according to the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of a main part of the MS / MS mass spectrometer of the present embodiment.

  A liquid chromatograph is provided in the front stage of the mass spectrometer, and a sample liquid separated by a liquid chromatograph column is introduced into the nozzle 1. Various components contained in the sample are ionized and pass through the sampling cone 2 in the process of vaporizing the solvent from the droplets of the sample liquid sprayed (electrosprayed) in an atmosphere of substantially atmospheric pressure while being given a charge offset from the nozzle 1. Then it is sent to the latter stage. The ions are converged when passing through the first ion lens 3 and the second ion lens 4, accelerated in some cases, and introduced into the first stage quadrupole 5. Although ions having various masses are introduced into the first stage quadrupole 5, only the target ions having a specific mass (strictly, the mass-to-charge ratio m / z) select the first stage quadrupole 5. The other ions are sent to the collision cell 6 at the next stage, and other ions are diverged on the way.

  A predetermined collision-induced dissociation (CID) gas such as argon gas is introduced into the collision cell 6, and the target ion is an electric field formed by a second-stage quadrupole 7 disposed in the collision cell 6. If it collides with CID gas when passing through, it will cleave. In other words, the target ions selected by the first stage quadrupole 5 become precursor ions, and various product ions are generated. These various product ions and target ions that have not been cleaved exit from the collision cell 6 and are introduced into the third stage quadrupole 8, and only product ions having a specific mass selectively select the third stage quadrupole 8. It passes through and is sent to the ion detector 9, and other ions diverge on the way. In this way, only product ions having a specific mass arrive at the ion detector 9 and a detection signal corresponding to the amount of the ions is output. By scanning the voltage applied to the third stage quadrupole 8, the mass of the product ions selected by the third stage quadrupole 8 can be scanned. Further, by changing the voltage applied to the first stage quadrupole 5, the mass of the ions selected by the first stage quadrupole 5, that is, the precursor ions can be changed.

  The path through which ions pass from the nozzle 1 to the ion detector 9 is divided into a plurality of rooms, and the quadrupoles 5, 7, 8 and the ion detector 9 are provided from the first stage ionization chamber where the nozzle 1 is disposed. Vacuum evacuation is performed so that the degree of vacuum increases stepwise toward the installed analysis chamber. However, since the CID gas is supplied into the collision cell 6 almost continuously, the gas pressure in the collision cell 6 is relatively high even in a high vacuum analysis chamber. For this reason, the ions colliding with the CID gas in the collision cell 6 are likely to diverge by changing the traveling direction, but the ions are appropriately focused near the ion optical axis C by the electric field formed by the second-stage quadrupole 7. Carried to the later stage. In the mass spectrometer of the present embodiment, a virtual quadrupole rod type ion guide having a characteristic structure described later is used as the second stage quadrupole 7.

  Next, the detailed structure of this virtual quadrupole rod type ion guide will be described with reference to FIGS. This virtual quadrupole rod type ion guide includes electrode members 11 and 12 and an electrode holder 13 as main components. FIG. 2 is a plan view of the first electrode member 11 and the second electrode member 12 as viewed from a direction parallel to the ion optical axis C.

  The first electrode member 11 shown in FIG. 2A is formed by processing a single metal plate (or other conductive plate member), and has an annular shape centered on the ion optical axis C. Part 20, a pair of electrode base plate parts 21 extending inwardly from the upper and lower sides of the inner peripheral edge of the annular part 20, that is, toward the ion optical axis C, and from the upper left of the outer peripheral edge of the annular part 20 And a terminal portion 22 extending outward. Four circular openings 23 are formed in the annular portion 20 at an angular interval of 90 °. The electrode base plate portion 21 has an elongated shape in which an edge facing the ion optical axis C is formed in an arc shape, and the arc-shaped edge ends of the two electrode base plate portions 21 are 180 ° across the ion optical axis C. Opposite.

  The second electrode member 12 shown in FIG. 2B is a member having exactly the same shape as the first electrode member 11, and the first electrode member 11 is rotated by 90 ° clockwise around the ion optical axis C in FIG. It has been made. However, in FIG. 2B, for convenience of explanation, reference numerals different from those in FIG.

  3A is a plan view of the electrode holder 13 viewed from a direction parallel to the ion optical axis C, and FIG. 3B is a cross-sectional view taken along the line AA ′ in FIG. (c) is sectional drawing in the BB 'arrow cutting line in (a). The electrode holder 13 is formed of an insulating synthetic resin (or another insulator) such as Teflon (trademark of DuPont), and has an annular portion 30 having a thickness in the direction of the ion optical axis C, and an annular portion. And a flange portion 31 projecting outward in an approximately L-shaped cross section from the outer peripheral edge of the outer periphery 30, and a notch portion 32 having a predetermined width is formed in the flange portion 31 at one location in the circumferential direction. In addition, four bolt insertion holes 33 are formed in the annular portion 30 at an angular interval of 90 °. The inner diameter of the bolt insertion hole 33 is slightly smaller than the inner diameter of the circular openings 23 and 27 of the electrode members 11 and 12. The diameter of the inner peripheral edge of the flange portion 31 is substantially the same as or slightly larger than the diameter of the outer peripheral edge of the annular portions 20 and 24 of the electrode members 11 and 12, and the width of the notch portion 32 is the terminal portions 22 and 26. The width is slightly larger.

  4A is a plan view of a virtual quadrupole rod type ion guide composed of the electrode members 11 and 12 and the electrode holder 13, as viewed from a direction parallel to the ion optical axis C, and FIG. It is sectional drawing in an EE 'arrow cutting line in the inside. FIG. 5 is a longitudinal sectional view of the main part showing the electrode arrangement of the virtual quadrupole rod type ion guide.

  By fitting the first electrode member 11 inside the flange portion 31 so that the terminal portion 22 coincides with the notch portion 32 of the electrode holder 13 described above, one first electrode member is provided in one electrode holder 13. 11 is held. In this state, the center of the circular opening 23 of the first electrode member 11 and the center of the bolt insertion hole 33 of the electrode holder 13 are both located on the same line parallel to the ion optical axis C. On the other hand, when the other electrode holder 13 is rotated 90 ° clockwise in FIG. 3A around the ion optical axis C, the position of the notch 32 coincides with the position of the terminal 26, so that the second electrode The member 12 is fitted inside the flange portion 31 similarly to the first electrode member 11.

In this way, the electrode holder 13 holding the first electrode member 11 and the electrode holder 13 holding the second electrode member 12 are alternately arranged in the direction of the ion optical axis C, and are adjacent to each other as shown in FIG. The electrode holders 13 are brought into close contact with each other. Then, the annular portions 20 and 24 of the first and second electrode members 11 and 12 are sandwiched between the flange portions 31 of the two adjacent electrode holders 13. A virtual quadrupole rod type ion guide is configured by stacking a predetermined number of electrode holders 13 holding the electrode member 11 or 12 in the direction of the ion optical axis C.

  When the plurality of electrode holders 13 are laminated in this way, the bolt insertion holes 33 of the electrode holders 13 and the circular openings 23 of the electrode members 11 and 12 are positioned on the ion optical axis C at 90 ° positions on the circumference. Align on parallel lines. Therefore, as shown in FIG. 4B, by passing the four fixing bolts 14 through the bolt insertion holes 33 in the direction parallel to the ion optical axis C, the electrode members 11 and 12 are moved as described above. The plurality of electrode holders 13 are fixed in a sandwiched state. Since the inner diameter of the circular opening 23 is larger than the inner diameter of the bolt insertion hole 33, even if the metal fixing bolt 14 is inserted into the bolt insertion hole 33, the bolt 14 and the electrode members 11, 12 do not contact each other. Insulation can be secured.

  Since the first electrode member 11 and the second electrode member 12 are rotated by 90 ° around the ion optical axis C, they are adjacent to a certain first electrode member 11 in the ion optical axis C direction. A total of four electrode base plate portions 21 and 25 provided on one second electrode member 12 are 90 ° symmetrically arranged around the ion optical axis C as shown in FIG. All edges facing the optical axis C are arcuate. The four electrode base plate portions 21 and 25 constitute a quadrupole quadrupole. Although these four poles do not exist on one plane orthogonal to the ion optical axis C (is present at a position shifted in the direction of the ion optical axis C), the conventional virtual quadruple shown in FIG. In the pole rod type ion guide, it has an action equivalent to that of the four electrode base plates existing on one surface orthogonal to the ion optical axis C. To realize the four-stage configuration shown in FIG. 10B, four electrode holders 13 holding the first electrode member 11 and four electrode holders 13 holding the second electrode member 12 are used. These may be arranged alternately in the direction of the ion optical axis C.

  In FIG. 6, six electrode holders 13 holding the first electrode member 11 and six electrode holders 13 holding the second electrode member 12 are used, and they are arranged alternately to form a six-stage configuration. Of things. The electrode base plate portion 21 of the first electrode member 11 and the electrode base plate portion 25 of the second electrode member 12 are separated by a distance d in the direction of the ion optical axis C, but this is determined by the thickness of the electrode holder 13. In other words, the distance d between the electrode base plate portion 21 and the electrode base plate portion 25 can be determined with high accuracy by the thickness of the electrode holder 13. Each of the six electrode base plates 21 or 25 arranged in the direction of the ion optical axis C constitutes one virtual rod electrode, and four virtual rod electrodes are arranged so as to surround the ion optical axis C, thereby providing a virtual. A quadrupole rod type ion guide is configured.

  For the virtual quadrupole rod type ion guide, for example, a composite voltage V + v · cosωt obtained by superimposing a high-frequency voltage v · cosωt on a DC voltage V is applied to the six first electrode members 11 to form six second electrodes. For example, a composite voltage Vv · cosωt obtained by superimposing a high-frequency voltage −v · cosωt on a DC voltage V is applied to the electrode member 12. As shown in FIG. 4A, these voltages can be applied from terminal portions 22 and 26 that protrude outward from the outer peripheral edge of the electrode holder 13. By applying the voltage as described above, a high-frequency electric field is formed in the space surrounded by the four virtual rod electrodes formed by the electrode base plate portions 21 and 25, and thereby ions are brought near the ion optical axis C. It can be transported to the subsequent stage while converging.

  FIG. 6 is a diagram showing a result of simulating the passage state of ions in the internal space of the virtual quadrupole rod type ion guide shown in FIG. As described above, this virtual quadrupole rod type ion guide does not have the four electrode plate portions 21 and 25 on the same plane. However, as can be seen in FIG. Transported while converging in the vicinity. Thereby, high ion transport efficiency can be achieved.

  Instead of applying the same composite voltage to the six first electrode members 11 and the six second electrode members 12, respectively, the DC voltage is changed stepwise in the direction of the ion optical axis C, so The ions can also be accelerated or decelerated by the field potential gradient.

  As described above, according to the virtual quadrupole ion guide in the mass spectrometer of the present embodiment, the same voltage is applied and the pair of electrode base plate portions facing each other across the ion optical axis C are connected. The connection part is formed of a single metal plate, and an ion guide can be configured by stacking a plurality of electrode holders holding the metal plate and fixing them with bolts. Less is required, and assembly and manufacturing / use adjustment are easy. Further, it is possible to easily change the number of stages, that is, the number of electrode base plate portions constituting one virtual rod electrode.

  In the configuration of the above embodiment, the four poles do not exist on one surface orthogonal to the ion optical axis C. However, the four poles can be arranged on one surface orthogonal to the ion optical axis C as follows. That is, the second electrode member 12 shown in FIG. 2B is used as it is, and the first electrode member shown in FIG. 7 having a slightly different shape from that of the above embodiment is used. In the first electrode member 15, an electrode base plate portion 41 extending inward from the inner peripheral edge of the annular portion 20 is bent into a bowl shape in the middle, and the inner peripheral portion of the electrode base plate portion 41 is an annular portion. 20 is parallel to 20 and shifted in the direction of the ion optical axis C.

  Thus, when the first electrode member 15 is held by the electrode holder 13 and a plurality of electrode holders 13 are stacked in the direction of the ion optical axis C, as in the above embodiment, the electrode base plate portion of the first electrode member 15 is stacked. The inner peripheral portion 41 and the electrode base plate portion 25 of the second electrode member 12 are located on one surface orthogonal to the ion optical axis C, and are arranged as shown in FIG.

  Moreover, although the said Example is an example using the virtual quadrupole rod type ion guide, it is also easy to increase the number of poles, such as a hexapole and an octupole. When the virtual hexapole rod type ion guide is configured, as shown in FIG. 9A, the electrode base plate portions 21 are spaced from the inner peripheral edge of the annular portion 20 around the ion optical axis C at intervals of 120 °. An electrode member having an extended shape is used. When a virtual octupole rod type ion guide is configured, as shown in FIG. 9 (b), the electrode base plate portion 21 is spaced from the inner peripheral edge of the annular portion 20 around the ion optical axis C at intervals of 90 °. An electrode member having an extended shape is used. On the other hand, the second electrode member may be obtained by rotating the first electrode member around the ion optical axis C by 60 ° and 45 °, respectively.

  In the above embodiment, the virtual multipole rod type ion guide characteristic of the present invention is used in the collision cell 6. However, various parts that conventionally used ion transport optical systems such as an ion guide and an ion lens were used. Can be used. For example, in the MS / MS mass spectrometer shown in FIG. 1, a virtual multipole rod ion guide can be used for the first ion lens 3 and the second ion lens 4. Needless to say, the present invention is not limited to the MS / MS type and can be used as an ion transport optical system in various mass spectrometers.

Claims (4)

2n (n is an integer of 2 or more) virtual rod electrodes made up of m (m is an integer of 2 or more) electrode base plates separated from each other in the direction of the ion optical axis are arranged so as to surround the ion optical axis. In a mass spectrometer equipped with a virtual multipole rod type ion transport optical system comprising:
The n electrode base plate portions that belong to every other virtual rod electrode around the ion optical axis and are arranged in a plane orthogonal to the ion optical axis are electrically connected to the n electrode base plate portions. Are formed integrally with one conductive plate as an electrode member, and the electrode members are arranged 2 m apart from each other in the direction of the ion optical axis, thereby arranging the virtual multipole rod ion transport optical system. A mass spectrometer characterized by comprising.   2. The mass spectrometer according to claim 1, wherein the electrode member has a shape in which the electrode base plate portion extends inward from an inner edge of the connection portion that is substantially annular. Any one of the electrode members is held by one insulating holding member that is inserted in order to separate a predetermined distance between two electrode members adjacent in the ion optical axis direction. The mass spectrometer according to claim 2. The 2 m electrode members include m first electrode members whose electrode base plate portions are flush with the connection portions, and m second electrodes whose electrode base plate portions are not flush with the connection portions. Each of the virtual rod electrodes, by arranging the first electrode members and the second electrode members alternately and apart in the direction of the ion optical axis at the position of the substantially annular connecting portion. The mass spectrometer according to claim 2, wherein a total of 2n electrode base plate portions are positioned on a plane orthogonal to the ion optical axis.

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